Risk analysis of 2-year mortality in elderly male military veterans with non-thyroidal illness syndrome​

Abstract Background: Elderly patients with non-thyroidal illness syndrome (NTIS) have relatively severe symptoms and a poor prognosis. However, there are few studies on the correlation between NTIS and mortality among hospitalised elderly patients. This study aimed to investigate the characterization of NTIS inpatients with biochemical indicators and mortality prediction.Methods: In the present study, 931 male veteran inpatients ≥ 60 years of age who visited our hospital from January 2012 to December 2013 were selected and divided into the NTIS group (n = 193) and normal thyroid function (non-NTIS) group（n = 738). Following propensity score matching to match the two groups according to age and body mass index, the NTIS group and non-NTIS group consisted of 192 and 660 patients, respectively. Data on biochemical indicators and mortality were collected. Results: Patients had more primary care and more respiratory disease and chronic kidney disease in the NTIS than in the non-NTIS group. Serum total protein (TP), albumin (Alb), prealbumin (PA), haemoglobin (Hb), uric acid (UA), triglyceride (TG), and high-density lipoprotein cholesterol (HDLC) levels were significantly lower, and fasting blood glucose (FBG) and urea nitrogen (UN) levels were higher, in the NTIS than in the non-NTIS group. Triiodothyronine, TP, Alb, and PA levels correlated positively with the Hb level and negatively with FBG, UN, and creatinine (Cr) levels. The free T3 level correlated positively with TP, Alb, PA, Hb, and UA levels and negatively with FBG, UN, and Cr levels. A lower free T3 level was associated with increased all-cause mortality after adjusting for covariates. Patients in the NTIS group had a lower survival rate at 6-month (78.65% vs. 97.73%), 1-year (68.23% vs. 96.97%) and 2-year (64.58% vs. 86.52%). Receiver operating characteristic curve (ROC) analysis showed that a cut-off free T3 level of 3.45 pmol/L yielded the highest sensitivity and specificity for predicting all-cause mortality at 2 years.Conclusion: Among elderly male inpatients, the survival rate was lower in the NTIS group. Serum protein levels and renal function decreased and the FBG level increased with decreasing triiodothyronine and free T3 levels. A decreased free T3 level in hospitalized elderly male patients was a predictor of poor prognosis.